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An astute family physician practicing in Huronsville is puzzled by a sudden increase in the number of patients who come to his practice complaining of hair loss. He has noted that over a six month period, there have 10 such cases and 6 of them have been prescribed Arzotec, a new non-sedating antihistaminic.

Through a contact at Huronsville Clinic, he finds that they too have noted a similar trend. In fact, an early look at their records shows that alopecia was noted in 6 out of 23 patients prescribed the drug. The same problem had been noted in 4 out of 50 patients who had not been prescribed the drug. The estimated odds ratio of 4.05 was worrisome enough to stimulate a larger prospective study .

A year later, the following results have been obtained:




No Alopecia

Drug Exposure



No Drug Exposure



Based on the above results, the attributable risk due to the drug is 0.08.


This problem is similar in format to an earlier one, A Rash to Judgement?. It serves to introduce students to basic epidemiological concepts, namely study designs and the rules of causation. It helps them tease out the meaning ofa number of commonly used terms.

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